Effect of estrogen on the expression of mRNAs of different actin isoforms in immature rat uterus. Cloning of alpha-smooth muscle actin message

Exogenous 17-β estradiol administration blunts progression of established angiotensin II-induced abdominal aortic aneurysms in female ovariectomized mice

Background

Abdominal aortic aneurysms (AAAs) occur predominately in males. However, AAAs in females have rapid growth rates and rupture at smaller sizes. Mechanisms contributing to AAA progression in females are undefined. We defined effects of ovariectomy, with and without 17-β estradiol (E2), on progression of established angiotensin II (AngII)-induced AAAs in female mice.

Methods

We used neonatal testosterone exposures at 1 day of age to promote susceptibility to AngII-induced AAAs in adult female Ldlr^−/− mice. Females were infused with AngII for 28 days to induce AAAs, and then stratified into groups that were sham, ovariectomized (Ovx, vehicle), or Ovx with E2 administration for 2 months of continued AngII infusions. Aortic lumen diameters were quantified by ultrasound and analyzed by linear mixed model, and maximal AAA diameters were analyzed by one-way ANOVA. Atherosclerosis was quantified en face in the aortic arch. AAA tissue sections were analyzed for cellular composition. We quantified effects of E2 on abdominal aortic smooth muscle cell (SMC) growth, α-actin and transforming growth factor-beta (TGF-β) production, and wound healing.

Results

Serum E2 concentrations were increased significantly by E2. Aortic lumen diameters increased over time in sham-operated and Ovx (vehicle) females, but not in Ovx females administered E2. At day 70, E2 administration decreased significantly aortic lumen diameters compared to Ovx vehicle and sham-operated females. Compared to Ovx females (vehicle), maximal AAA diameters were reduced significantly by E2. AAA tissue sections from Ovx females administered E2 exhibited significant increases in α-actin and decreases in neutrophils compared to Ovx females administered vehicle. In abdominal aortic SMCs, E2 resulted in a concentration-dependent increase in α-actin, elevated TGF-β, and more rapid wound healing. E2 administration to Ovx females also significantly reduced atherosclerotic lesions compared to sham-operated females. This effect was accompanied by significant reductions in serum cholesterol concentrations.

Conclusions

E2 administration to Ovx females abolished progressive growth and decreased severity of AngII-induced AAAs. These effects were accompanied by increased SMC α-actin, elevated TGF-β, and reduced neutrophils. Similarly, E2 administration reduced AngII-induced atherosclerosis. These results suggest that loss of E2 in post-menopausal females may contribute to progressive growth of AAAs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-015-0030-1) contains supplementary material, which is available to authorized users.

Chronic nicotine exposure stimulates biliary growth and fibrosis in normal rats

BACKGROUND

Epidemiological studies have indicated smoking to be a risk factor for the progression of liver diseases. Nicotine is the chief addictive substance in cigarette smoke and has powerful biological properties throughout the body. Nicotine has been implicated in a number of disease processes, including increased cell proliferation and fibrosis in several organ systems.

AIMS

The aim of this study was to evaluate the effects of chronic administration of nicotine on biliary proliferation and fibrosis in normal rats.

METHODS

In vivo, rats were treated with nicotine by osmotic minipumps for two weeks. Proliferation, α7-nicotinic receptor and profibrotic expression were evaluated in liver tissue, cholangiocytes and a polarized cholangiocyte cell line (normal rat intrahepatic cholangiocyte). Nicotine-dependent activation of the Ca(2+)/IP3/ERK 1/2 intracellular signalling pathway was also evaluated in normal rat intrahepatic cholangiocyte.

RESULTS

Cholangiocytes express α7-nicotinic receptor. Chronic administration of nicotine to normal rats stimulated biliary proliferation and profibrotic gene and protein expression such as alpha-smooth muscle actin and fibronectin 1. Activation of α7-nicotinic receptor stimulated Ca(2+)/ERK1/2-dependent cholangiocyte proliferation.

CONCLUSION

Chronic exposure to nicotine contributes to biliary fibrosis by activation of cholangiocyte proliferation and expression of profibrotic genes. Modulation of α7-nicotinic receptor signalling axis may be useful for the management of biliary proliferation and fibrosis during cholangiopathies.

Smooth muscle cells of the bovine cervical stroma may have a secretory, rather than a contractile function during parturition

The bovine cervix contains a large amount of smooth muscle cells distributed over an outer muscular layer and within a stromal layer. The stromal layer exhibits no electromyographic (EMG) activity at parturition. This leads to the question whether the stromal smooth muscle cells of the bovine cervix are prepared to contract with parturition, or whether they have another function. To this end, cervical biopsies were repeatedly taken from 10 pregnant cows at day-185 and -275 of gestation, at spontaneous, uncomplicated calving and at 30 days after calving. The smooth muscle bundles of the stroma were immunohistochemically analysed (n = 5) with regard to their integrity and cellular density, and the degree of staining for connexin-43, smooth muscle actin alpha (SMA), desmin and vimentin. Additionally, the mRNA expression for connexin-43, SMA, desmin and vimentin was determined with RT-PCR (n = 5). The smooth muscle tissue was arranged in bundles, also at parturition. However, the cellular density of these bundles and the SMA mRNA expression were decreased at parturition. Additionally, the SMA staining and connexin-43 expression and staining remained constant during pregnancy and at parturition. This might indicate that stromal smooth muscle cells are not prepared to contract with parturition, in contrast to the myometrial smooth muscle cells. The smooth muscle cells, stained for SMA, also expressed vimentin, and the proportion of co-expression was increased at day-275 of pregnancy. This suggests that the stromal smooth muscle cells predominantly have a secretory function in cows.

Development and validation of endogenous reference genes for expression profiling of medaka (Oryzias latipes) exposed to endocrine disrupting chemicals by quantitative real-time RT-PCR

The quantitative real-time reverse transcription polymerase chain reaction (Q-RT-PCR) technique has been increasingly used in endocrine disrupting chemicals (EDCs) research. Usually, an appropriate endogenous control gene is critical for Q-RT-PCR to normalize the errors and sample-to-sample variations that occur in the course of tissue collection, RNA isolation, and RT-PCR. In this study, we cloned ribosomal protein L7 (RPL-7) from medaka (Oryzias latipes), and then used Q-RT-PCR to study its transcription characteristics and those of glyceraldehyde-3-phosphate dehydrogenase, beta-actin, mitochondrial 16S ribosomal RNA (16S rRNA), and 18S rRNA. Of the five genes, RPL-7 and 18S rRNA were expressed with the less variance among the same tissue samples, in different tissues, and stages of development and were unaffected by EDCs exposure. The expression levels of RPL-7 among different tissues were between 9.76 x 10(6) +/- 9.49 x 10(5) and 1.39 x 10(7) +/- 1.69 x 10(6) copies/microg RNA but those of 18S rRNA were as high as 4.48 x 10(11) +/- 5.95 x 10(10) to 5.90 x 10(11) +/- 1.21 x 10(10) copies/microg RNA, which is above the usual detection scope of Q-RT-PCR if no complementary DNA reaction dilution is performed. As a result, RPL-7 is the single suitable endogenous control gene for expression profiling in future studies, especially in studies on the EDCs issue using medaka.

Sexually dimorphic gene expression in the hypothalamus, pituitary gland, and cortex

We examined sex differences in the transcriptomes of hypothalamus, pituitary gland, and cortex of male and female mice using serial analysis of gene expression. In total 940,669 tags were sequenced. In hypothalamus, 3 transcripts are differentially expressed by gender, including growth hormone (neuromodulation) and 3beta-hydroxysteroid dehydrogenase-1 (steroidogenesis). In pituitary gland, 43 transcripts are differentially expressed, including RAS guanyl-releasing protein 2 (cell signaling), ornithine transporter (mitochondrial transport), H3 histone family 3B (chromatin structure), heterogeneous nuclear ribonucleoprotein U (chromatin remodeling), NADH dehydrogenase (mitochondrial oxidative phosphorylation), neuronatin (cell differentiation), and ribosomal protein S27a (protein metabolism). EST X (inactive)-specific transcript antisense is expressed at a higher level in the three female organs, whereas growth hormone and NADH dehydrogenase are expressed at higher levels in female cortex. Thus, the current study has characterized key sexual dimorphisms in the transcriptomes of the hypothalamus, pituitary, and cortex.

Expression and Localization of Alpha-Smooth Muscle and Gamma-Actins in the Pregnant Rat Myometrium1

The myometrium undergoes dramatic changes as pregnancy progresses through phases of proliferation, hypertrophy, contractile state and labor. In this study, we showed that the composition of the muscle actin isoforms, a major component of the myometrial contractile apparatus and cytoskeleton, was modified during pregnancy. The expression of smooth muscle alpha-actin (Acta2, which we abbreviate as alpha-SM-actin) and gamma-actin mRNAs and proteins was examined by real-time polymerase chain reaction and Western immunoblot, and was localized with immunohistochemistry, in the nonpregnant, pregnant, and postpartum rat uterus. Both alpha-SM-actin (vascular specific actin isoform) and gamma-actin (predominant in visceral smooth muscle) were detected in the rat myometrium. Myometrial expression of alpha-SM-actin mRNA and protein was high throughout pregnancy. The transcript and protein levels of gamma-actin were increased significantly in the second part of gestation (31.8-fold increase for mRNA and 16.7-fold increase for protein relative to nonpregnant). The localization of gamma-actin was markedly altered during pregnancy. In early gestation, myometria from empty and gravid uterine horns of the unilaterally pregnant rats showed abundant gamma-actin immunostaining in the longitudinal layer but weak staining in the circular layer. Gamma-actin immunostaining increased in only the circular layer of the gravid horn after midgestation and remained low in the empty one. Gamma-actin protein translocated to the membranous region of uterine myocytes at late gestation. The temporal alteration in gamma-actin expression and localization at late gestation suggested that this change in myometrial composition of contractile proteins is important to adequately prepare the myometrium for the development of optimal contractions during labor.

Estrogen and Postnatal Maturation Increase Caveolar Number and Caveolin-1 Protein in Bladder Smooth Muscle Cells

PURPOSE

Clinical studies indicate that detrusor contractility decreases in old age and the dense band pattern with caveolar depletion represents the ultrastructural norm of the aged human detrusor. We performed animal studies to explore the hypothesis that lowering estrogen induces the dense band pattern with estrogen replacement restoring usual sarcolemmal appearance and increasing caveolar number.

MATERIALS AND METHODS

Newborn, young (1-month-old) and middle-aged (13 to 14-month-old) female rats were studied. Middle-aged animals were evaluated 4 months after sham operation or ovariectomy (OVx) with OVx rats receiving placebo or 25% 17beta-estradiol (E2) capsules for 1 week prior to sacrifice. Electron microscopy was used to evaluate sarcolemmal structure and quantify caveolar numbers in bladder muscle cells. Caveolae were also assessed by measuring caveolin-1 protein.

RESULTS

Alternating electron dense and thinner zones with abundant caveolae were present in bladder sarcolemma from middle-aged animals. Newborn and OVx sarcolemma showed many ultrastructural features of the dense band pattern with fewer caveolae present per micro sarcolemma or per muscle cell compared with sham operated middle-aged controls. E2 replacement decreased the dense band pattern and increased caveolar numbers in OVx animals. Caveolin-1 protein levels underwent similar changes following maturation, OVx and E2 replacement, while alpha-smooth muscle actin remained unchanged.

CONCLUSIONS

Prolonged estrogen withdrawal results in sarcolemmal changes in middle-aged animals, similar to the dense pattern observed in newborns. Estrogen replacement decreases the dense pattern, while increasing caveolar numbers and caveolin-1 protein. It remains to be seen whether estrogen influences caveolar depletion and/or contractility in human bladders.

Differential binding of an SRF/NK-2/MEF2 transcription factor complex in normal versus neoplastic smooth muscle tissues

The malignant potential of smooth muscle tumors correlates strongly with the disappearance of gamma-smooth muscle isoactin, a lineage-specific marker of smooth muscle development. In this paper, we identify a 36-base pair regulatory motif containing an AT-rich domain, CArG box, and a non-canonical NK-2 homeodomain-binding site that has the capacity to regulate smooth muscle-specific gene expression in cultured intestinal smooth muscle cells. Serum-response factor associates with an NK-2 transcription factor via protein-protein interactions and binds to the core CArG box element. Our studies suggest that the NK-2 transcription factor that associates with serum-response factor during smooth muscle differentiation is Nkx2-3. Myocyte-specific enhancer factor 2 binding to this regulatory complex was also observed but limited to uterine smooth muscle tissues. Smooth muscle neoplasms displayed altered transcription factor binding when compared with normal myometrium. Differential nuclear accessibility of serum-response factor protein during smooth muscle differentiation and neoplastic transformation was also observed. Thus, we have identified a unique regulatory complex whose differential binding properties and nuclear accessibility are associated with modulating gamma-smooth muscle isoactin-specific gene expression in both normal and neoplastic tissues.

Tissue-specific regulation of erythropoietin production in the murine kidney, brain, and uterus

Erythropoietin (Epo) produced by the kidney regulates erythropoiesis. Recent evidence suggests that Epo in the cerebrum prevents neuron death and Epo in the uterus induces estrogen (E(2))-dependent uterine angiogenesis. To elucidate how Epo expression is regulated in these tissues, ovariectomized mice were given E(2) and/or exposed to hypoxia, and the temporal patterns of Epo mRNA levels were examined. Epo mRNA levels in the kidney and cerebrum were elevated markedly within 4 h after exposure to hypoxia. Although the elevated level of Epo mRNA in the kidney decreased markedly within 8 h despite continuous hypoxia, the high level in the cerebrum was sustained for > or = 24 h, indicating that downregulation operates in the kidney but not in the brain. E(2) transiently induced Epo mRNA in the uterus but not in the kidney and cerebrum. Interestingly, the uterine Epo mRNA was hypoxia inducible only in the presence of E(2). Thus Epo expression appears to be regulated in a tissue-specific manner, endorsing the tissue-specific functions of Epo.

Expression of insulin-like growth factor binding protein-4, insulin-like growth factor-I receptor, and insulin-like growth factor-I in the mouse uterus throughout the estrous cycle

Recent evidence suggests that a regulated insulin-like growth factor (IGF) system mediates the effects of estrogen, promoting the proliferation and differentiation of specific uterine cell types throughout the estrous cycle and during gestation in the rodent. Previous studies have shown that IGFs are differentially expressed in the mouse uterus during the periimplantation period. In the current study, we examined the expression of IGF binding protein-4 (IGFBP-4), IGF-I receptor (IGF-IR), and IGF-I in the mouse uterus throughout the estrous cycle. Ligand blot analysis was conducted on uterine homogenates using [125I]IGF-I. IGFBP-4 was detected in all uterine homogenates, varying in intensity throughout the estrous cycle. In situ hybridization studies at metestrus and diestrus demonstrated an intense IGFBP-4 mRNA signal in antimesometrial stromal cells between the luminal epithelium and the myometrium, but at proestrus and estrus, no IGFBP-4 signal was detected. No IGF-I mRNA was detected at any stage of the estrous cycle by in situ hybridization. However, by RT-PCR analysis, IGF-I mRNA was detected at all stages of the estrous cycle. RT-PCR analysis also showed IGF-IR mRNA throughout the estrous cycle. Using immunohistochemistry, IGF-IR immunostaining was detected throughout the estrous cycle and on days 2-7 of gestation, but was restricted to the glandular epithelium. These results suggest that uterine IGFBP-4 expression may not be dependent on uterine IGF-I expression. They also suggest that IGFBP-4 may play a role in uterine physiology independent of the inhibition of IGF-I action, and that IGF-IR is constitutively expressed in the mouse uterus.

Hormonal regulation of the estrogen receptor in primary cultures of hepatocytes from female rats

Estrogen treatment affects the hepatic synthesis and/or secretion of several proteins involved in clinically important pathological processes such as atherosclerosis, hypertension, and thrombosis. The endocrine regulation of the estrogen receptor (ER) concentration in primary cultures of rat hepatocytes was studied. Human growth hormone (hGH) and dexamethasone (DEX) in combination increased ER concentration 6-fold and ER mRNA levels 2.5-fold. These effects were not significantly different from those observed after treatment with the purely somatogenic bovine growth hormone (GH) in combination with DEX. Treatment with the lactogen ovine prolactin in the presence or absence of DEX did not significantly affect ER or ER mRNA concentrations. Triiodothyronine treatment at the most effective concentration (50 nM) increased ER and ER mRNA levels twofold. Medium supplementation with estradiol (0.1 nM) throughout the experiment did not affect the response to treatment with hGH and DEX. Treatment with high concentrations of ethinylestradiol in combination with hGH and DEX, however, increased the ER level twice as much as hGH and DEX without addition of estradiol or ethinylestradiol, whereas the ER mRNA concentration was the same in both the GH+DEX group and GH+ DEX+ (estradiol or ethinylestradiol) groups. These data indicate the importance of GH in combination with glucocorticoids for the maintenance of ER concentrations in the rat liver. Thyroid hormones may be of some, although minor importance, whereas the data suggest that prolactin is not directly involved in hepatic ER regulation.

Isolation and characterization of a novel short chain alcohol dehydrogenase-like isozyme by differential display of distinct smooth muscle cell phenotypes

Gastrointestinal smooth muscle development proceeds by the linear differentiation of distinct smooth muscle cell phenotypes. In an effort to identify specific gene products associated with distinct smooth muscle cell phenotypes, we performed differential display on smooth muscle myoblasts versus immature smooth muscle myocytes. This analysis identified a novel short-chain alcohol dehydrogenase-like isozyme which was preferentially expressed in smooth muscle myoblasts over immature and mature smooth muscle myocytes. We postulate that this novel short-chain alcohol dehydrogenase-like isozyme may play a role in potentiating the dedifferentiation of smooth muscle cells in vitro.

Molecular marker for development of interstitial cystitis in rat model: isoactin gene expression

PURPOSE

To determine whether the differential expression of bladder smooth muscle isoactin can be used as a molecular marker for the development of interstitial cystitis (IC).

METHODS

Three groups of five female Sprague-Dawley rats each underwent urethral catheterization and intravesical instillation of 0.5 ml. of 0.4N HCl. One group was sacrificed one, two and four weeks after the application of HCl, and their bladders harvested for histologic examination and evaluation using Northern blot analysis of bladder smooth muscle isoactins. Five control animals were sacrificed and their bladders harvested to establish isoactin gene expression of bladder smooth muscle in the normal state. The bladders of the rats in each group were excised, immediately frozen in liquid nitrogen, pooled, then stored -70 degrees C until needed for RNA isolation. Isoactin cDNA probes have been developed, therefore isoactin specific cDNA insert fragments were isolated and insert DNA was purified by gel electrophoresis. Total cellular RNA was isolated from 1.0 gm. of bladder smooth muscle from each group. After spectrophotometric quantification, Northern Blot analysis was performed using 2% agarose-formaldehyde gels and Biotrans nylon membranes. Two complete Northern Blot series were run on a single gel and blotted to a single membrane to eliminate gel and blotting discrepancies.

RESULTS

Microscopic histologic analysis revealed detrusor mastocystosis and eosinophilia as has been noted in humans with chronic interstitial cystitis. Two weeks after the intravesical application of hydrochloric acid, the relative expression of gamma-smooth muscle isoactin was noted to increase by 1.7-fold, while alpha-smooth muscle isoactin expression increased by a factor of 9. These effects were seen to stabilize four weeks after acid application.

CONCLUSIONS

The intravesical application of dilute HCl in rats results in a histologic appearance which mimics that seen in humans with interstitial cystitis. The appearance of detrusor mastocytosis and eosinophilia was accompanied by a relative decrease in the expression of gamma- and a relative increase in alpha-smooth muscle isoactin gene expression. This pattern of smooth muscle isoactin expression is consistent with a more immature and possibly synthetic smooth muscle phenotype, which may be responsible for the clinical presentation of those with IC. Northern blot analysis of bladder smooth muscle cells may serve as an effective marker for the development of interstitial cystitis in humans.

Dexamethasone attenuates the estradiol-induced increase of IGF-I mRNA in the rat uterus

In recent years growth factors, e.g. insulin-like growth factor-I (IGF-I), transforming growth factor-alpha (TGF-alpha) and epidermal growth factor (EGF), have been considered as mediators of estradiol-stimulated growth in the uterus. In the liver, dexamethasone (Dex) has been shown to inhibit the IGF-I mRNA increase induced by growth hormone (GH). In the present study the influence of Dex on estradiol-stimulated induction of uterine IGF-I mRNA was examined. The concentration of IGF-I mRNA in the uterus and liver was monitored, as well as the levels of ER mRNA and estrogen receptor (ER). Since it has been previously shown that the maximal induction of uterine IGF-I mRNA after estradiol (E2) stimulation occurs after 21-24 h, Dex was administered to ovariectomized (ovx) rats 3 h before an E2 injection and 24 h before sacrifice. There was a significant decrease in IGF-I mRNA in the Dex+E2 treated rats compared to the rats given E2 only. In both groups an increase was seen compared to the level in the ovx control group. The uterine ER mRNA levels in E2 and Dex+E2 treated animals were significantly elevated compared to the ovx control. There were no significant changes in uterine ER content after hormone treatment compared to the level in ovx control rats. In the liver no effects on IGF-I mRNA were detected. Hepatic ER mRNA was significantly increased in the E2 treated group, compared to both the ovx control group and the animals that received Dex+E2. The hepatic ER level was also increased in the E2 treated group compared to the ovx control and the group which received Dex+E2. In conclusion, Dex does attenuate the estrogen-induced uterine IGF-I mRNA increase in ovx rats. In addition to this, Dex was found to inhibit the estrogen-induced increase in ER and ER mRNA in the liver of ovx rats.

Role of 17 beta-estradiol and progesterone in the regulation of synthesis and secretion of chorionic gonadotropin by the first trimester human placenta

The role of 17 beta-estradiol and progesterone in the regulation of synthesis of chorionic gonadotropin (CG) by first trimester human placenta has been studied using 1,4,6 androstatriene 3-17-dione to block the synthesis of 17 beta-estradiol or tamoxifen to block its action at receptor level and RU486 to block the action of progesterone at the receptor level. Results indicate that the synthesis of CG is negatively modulated by 17 beta-estradiol and positively modulated by progesterone as judged by the change in the levels of immunoreactive CG, alpha- and beta-CG mRNA and in vitro translation, as well as biosynthesis of alpha- and beta-CG and, finally, nuclear run off transcription.

Gap junction regulation in the uterus and ovaries of immature rats by estrogen and progesterone

The effects of estrogen (E2) and progesterone (P) were examined on the expression levels of multiple gap junction (GJ) gene products (alpha 1 = Cx43, beta 1 = Cx32, beta 2 = Cx26) in the uterus and ovaries of immature rats by immunohistochemistry, electron microscopy and northern blot analysis. E2 induced the expression of alpha 1 connexin in the uterus (specifically in the myometrium and in endometrial stroma proximal to luminal epithelium) and ovaries. The E2-induced alpha 1 expression was completely suppressed by P in the uterus, but only partly in ovaries. Steroid hormones also modulated the quantity, size, and distribution of beta 1 and beta 2 containing junctional plaques along lateral cell borders in polarized luminal and glandular uterine epithelia. Small GJs were detected at basolateral regions in proliferative luminal epithelium following administration of E2. In contrast, large GJs were localized at subapical-lateral cell borders of the secretory epithelium following P-treatment. The co-administration of E2 + P had a synergistic effect on beta 1 and beta 2 expression in the luminal epithelium, but an inhibitory effect on beta 2 expression in glandular epithelium. Myometrial GJs were detected in freeze-fracture replicas as aggregates containing regularly arranged particles with particle free zones. In contrast, GJs in secretory epithelium contained particles which were arranged in a non-crystalline fashion. These GJs contained domains of mixed and segregated beta 1 and beta 2 antigens within a single plaque as revealed by laser scanning confocal microscopy analysis of immuno-double-labeled secretory epithelium. The demonstration of segregated antigens within a single GJ plaque indicates the possibility of multiple channel populations formed by homo-oligomeric connexons. These results suggest that different connexins can be differentially regulated by steroid hormones in different cell types, and that the same steroid hormone can have different effects on the same connexin in different cell types.

Androgen regulation of the insulin-like growth factor-I and the estrogen receptor in rat uterus and liver

For the first time testosterone is shown to be an important regulator of the insulin-like growth factor-I (IGF-I) in the rat uterus under in vivo conditions. In this study the regulation of IGF-I and the estrogen receptor (ER) by gonadal steroids in the uterus and liver of female rats was monitored. The ER level was assayed by hormone binding after treatment with testosterone, 5 alpha-dihydrotestosterone or estradiol and specific mRNA species were analyzed by a solution hybridization/RNase protection assay using 35S-labeled RNA probes. Ovariectomized rats restored uterine weight after treatment with testosterone. Uterine IGF-I mRNA was more than 20-fold higher in testosterone treated rats compared to untreated ovariectomized controls after 48 h treatment. The effects of testosterone on ovariectomized animals was followed in a timecourse study. Testosterone administration increased uterine IGF-I mRNA expression during the first 48 h and the maximally induced level was maintained throughout the duration of the experiment (168 h). Since induction of IGF-I mRNA by estrogen is transient, these data indicate that androgen and estrogen increase IGF-I mRNA by different mechanisms. Regulation of IGF-I mRNA by gonadal steroids was also studied in hypophysectomized animals. The rats were given either testosterone, 5 alpha-dihydrotestosterone or estradiol, and uterine IGF-I mRNA was measured after 1 week of treatment. At this timepoint estrogen treated rats showed levels of IGF-I mRNA not significantly different from those of hypophysectomized controls. In contrast testosterone and 5 alpha-dihydrotestosterone increased the IGF-I mRNA level 30 and 40 times, respectively, relative to hypophysectomized control animals. Since 5 alpha-dihydrotestosterone is not convertable to estrogen, the induction by testosterone was considered to be a true androgenic phenomenon.

Estrogen regulation of the estrogen receptor and insulinlike growth factor-I in the rat uterus: a potential coupling between effects of estrogen and IGF-I

The interrelationship between estrogen and insulin-like growth factor-I (IGF-I) in the regulation of uterine growth was studied in the rat. The levels of the estrogen receptor (ER), ER mRNA, and IGF-I mRNA in rat uterus and liver were monitored. Uterine ER in normal cycling rats was highest in proestrus and diestrus, as was IGF-I mRNA. ER mRNA and plasma estradiol peaked in proestrus. Hepatic ER mRNA and IGF-I mRNA were highest in diestrus, whereas ER was not significantly changed during the estrous cycle. The temporal effects of multiple injections or continuous infusion of 17 beta-estradiol in ovariectomized rats were examined. In the uterus of animals subjected to multiple injections, a 10-fold increase in IGF-I mRNA was seen 24 h after the start of the treatment, whereas rats given continuous infusion of estradiol showed a more than 16-fold increase. In both groups, the increase of IGF-I mRNA was transient although estrogen treatment was continued. To study local hormonal effects, ovariectomized rats were given estradiol in vaginal implants. The uterine IGF-I mRNA level increased two-fold in 3 days. The ER mRNA level increased 1.5-fold and the uterine weights were doubled. The plasma estradiol concentration did not change during the treatment. A separate experiment was carried out to establish whether IGF-I itself exercises estrogen-like effects. Ovariectomized rats were given hrIGF-I in osmotic minipumps for 3 days. The uteri of the treated animals weighted significantly more than did the controls. Quantitation of the level of uterine estrogen receptors revealed a significant decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in the expression of the beta-cytoplasmic and the gamma-smooth muscle actins in hypertrophied urinary bladder smooth muscle

The obstruction of the bladder outlet induces a marked increase in bladder mass, and this is accompanied by reduced contractility of bladder smooth muscle and alteration in the cellular architecture. In this study, we show that the composition of various isoforms of actin, a major component of the contractile apparatus and the cytoskeletal structure of smooth muscle, is altered in response to the obstruction-induced bladder hypertrophy. Northern blot analysis of the total RNA isolated from hypertrophied urinary bladder muscle, using a cDNA probe specific for smooth muscle gamma-actin, shows over 200% increase in the gamma-actin mRNA. However, the estimate of the amount of actin from the 2D gel reveals only a 16% increase in gamma-actin, since the 2D gel electrophoresis does not distinguish gamma-smooth muscle actin from gamma-cytoplasmic actin. The bladder smooth muscle alpha-actin and the smooth muscle alpha-actin mRNA are not altered in response to the hypertrophy. The obstructed bladder also reveals a decrease in the beta-cytoplasmic actin (37%) and a concomitant diminution in the beta-cytoplasmic actin mRNA (29%). Hence, the composition of the actin isoforms in bladder smooth muscle is altered in response to the obstruction-induced hypertrophy. This alteration of the actin isoforms is observed at both the protein and mRNA levels.

Regulation of estrogen receptor protein and messenger ribonucleic acid by estradiol and progesterone in rat uterus

The objective of this study was to examine the mechanisms of estrogen receptor (ER) processing and replenishment in the uterus of ovariectomized rats after estradiol and progesterone treatment. Uterine ER binding activity, ER protein and ER mRNA were measured by receptor binding exchange assay, Western blot and slot blot, respectively. The regulation of ER levels in rat uterus by estradiol and progesterone was very dramatic. Changes in ER protein were faithfully reflected by changes in binding activity. Estradiol caused receptor "processing" within 4 h of administration followed by recovery or "replenishment" of ER levels to the initial level by 20 h. The term "processing" has previously been used to describe the loss of ER binding activity in the early phase of estradiol-action, but it was never clear whether the ligand binding site was inactivated by processing or if the receptor molecule actually disappeared. This study shows that receptor "processing" constitutes disappearance of receptor protein and the later "replenishment" phase represents new ER protein rather than recycling of "processed" receptor. Progesterone-action, on the other hand, influenced only the "replenishment" phase by blocking recovery of ER protein. ER mRNA was suppressed by estradiol at 8 h, after the receptor was "processed" and "replenishment" already initiated. Progesterone, on the other hand, did not alter the steady state level of the message. Other mechanisms, such as regulation of translation rate of existing mRNA and changes in the rate of degradation of ER proteins are more likely involved in acute regulation of ER by these ovarian steroid hormones.

Effect of androgen on the expression of gap junction and beta-actin mRNAs in adult rat motoneurons

Expression of gap junction and beta-actin mRNAs was examined in androgen-sensitive motoneurons of the spinal nucleus of the bulbocavernosus (SNB) in adult male rats by in situ hybridization histochemistry using complementary DNAs encoding rat liver gap junction protein (connexin 32) and chick beta-actin. Hybridizable gap junction and beta-actin mRNAs were localised on the somata and proximal dendrites of SNB motoneurons. Removal of androgen by castration significantly reduced the expression levels of both gap junction and beta-actin mRNAs in the SNB motoneurons, whereas these changes were prevented by testosterone treatment. On the contrary, castration or testosterone treatment did not induce any changes in the expression levels of gap junction and beta-actin mRNAs in the motoneurons of the retrodorsolateral nucleus (RDLN), which accumulate androgen less frequently and sparsely than those in the SNB. These results suggest that androgen regulates the expression of both gap junction and beta-actin genes in the SNB motoneurons and may provide evidence for the molecular mechanisms of hormonally induced neuronal plasticity in the SNB motoneurons.

Transcriptional activation of jun and actin genes by estrogen during mitogenic stimulation of rat uterine cells

Estrogens induce transcriptional activation of c-fos and c-myc proto-oncogenes during mitogenic stimulation of human, chicken, mouse and rat cells in vivo and in vitro. In this paper we show that 17 beta-estradiol injected into adult ovariectomized rats increases c-jun, jun-B and jun-D gene transcription in the uterus. Kinetics and amplitude of response are different for each gene, since c-jun is activated first, within 30 min after injection, followed by jun-D and jun-B, 60 and 90 min after injection, respectively. Maximal activation of jun-B marks a drop in transcription of all the jun genes. Furthermore, transcriptional activation by 17 beta-estradiol of the growth-regulated beta- and gamma-cytoskeletal actin genes is prevented by an inhibitor of protein synthesis, indicating that it is a secondary response to the hormone. These data support the hypothesis that during growth stimulation of target cells the estrogen receptor induces transcription of regulatory genes, triggering in this way a cascade of gene regulation events that results in progression through the cell cycle.

Gestational modulation of myometrial proteins in the timed-pregnant Sprague-Dawley rat

These studies sought to test the hypothesis that the expression of myometrial proteins is modulated as the onset of parturition approaches. Myometrial proteins from timed-pregnant rats were analyzed utilizing sodium dodecylsulfate polyacrylamide gel and 2-dimensional electrophoresis, and Western blot techniques. SDS-PAGE gels demonstrated increased expression of at least 10 protein bands from 17 to 200+ KD. 2-dimensional gels confirmed the presence of at least five groups of gestationally modulated proteins. Western blots for phosphoinositide-specific phospholipase C demonstrated significant modulation of the expression of three isozymes. These studies have confirmed differential expression of myometrial proteins near term in the timed-pregnant rat; some of which play an important role in intracellular signal transduction in response to hormones and pharmacologic agents.

Complement C3 synthesis, peroxidase activity and eosinophil chemotaxis in the rat uterus: effect of estradiol and testosterone

Treatment of immature rats with estradiol (E2) produced a large increase in uterine peroxidase activity which was accompanied by an increase in eosinophil chemotactic factor (ECF-U). The synthesis of complement C3 was also induced in the uterus and the amount of this 180 kDa protein was determined both by immunoprecipitation and after separation by polyacrylamide gel electrophoresis. Testosterone (T) did not produce an increase in any of these parameters although it antagonized the estrogen-induced increase in uterine peroxidase activity and these effects were more pronounced in estrogen-primed animals. This antagonism was prevented by the antiandrogen, flutamide. Testosterone showed little effect on eosinophil chemotactic activity and did not inhibit the E2-stimulated synthesis of C3. The results with T were supported by the lack of any significant effect by flutamide which antagonizes receptor-mediated androgenic events. These findings are discussed in relation to the action of other types of hormonal steroids (progesterone, dexamethasone) in inhibiting these estrogen-induced molecular changes in the rat uterus and contribute to our understanding of steroid-steroid interaction and the regulation of uterine function.

Regulatory effects of growth hormone, glucocorticoids, and thyroid hormone on the estrogen receptor level in the rat liver

The multihormonal regulation of the estrogen receptor in the liver of female rats was studied under in vivo conditions. The steroid receptor level was assayed by hormone binding and specific mRNA analyzed by solution hybridization using a 35S-labeled RNA probe complementary to the ligand-binding domain of the estrogen receptor gene. Serum growth hormone levels were measured and correlated to the effects of glucocorticoid and thyroid hormone administration on the estrogen receptor expression. In animals subjected to adrenalectomy plus thyroidectomy, the estrogen receptor concentration was reduced from 59 fmol/mg cytosol protein to 10 fmol/mg protein (i.e., with 87% relative to control animals). Adrenalectomy or thyroidectomy alone caused a decrease with 14% and 66%, respectively. Substitution with 10 micrograms betamethasone and 1 microgram triiodothyronine daily for 9 days completely restored the receptor content to control levels. Substitution with either hormone alone increased, but only partially restored receptor levels. The effect of betamethasone alone was dose dependent from 10 micrograms/d to 100 micrograms/d. This dose dependence was not seen when the animal simultaneously received 1 microgram of triiodothyronine. Superphysiologic doses of triiodothyronine did not raise estrogen receptor levels above those seen in animals treated with physiologic doses. High doses of triiodothyronine (greater than 20 micrograms/d) decreased serum growth hormone levels. The estrogen receptor mRNA levels in livers from hypophysectomized animals were increased after treatment with growth hormone (2.5-fold), thyroid hormone (two-fold), and glucocorticoids (1.5-fold). The results obtained indicate a very complex regulation of liver estrogen receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison on collagen gene expression in the developing chick embryo tendon and heart. Tissue and development time-dependent action of dexamethasone

Glucocorticoids modulate various cellular functions such as proliferation, energy metabolism and the synthesis of proteins. In the present study, the response of collagen genes to dexamethasone in different stages of chick embryo development was studied in tendon and heart using Northern blot analysis and specific cDNA probes. The changes in collagen gene expression were compared to alterations in two reference mRNAs: actin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The levels of specific mRNAs measured per ribosomal RNA in tendon and heart varied markedly during normal development. In tendon the relative levels of alpha 1(I), alpha 2(I) and alpha 1(III) collagen mRNAs were highest between days 14-16 when also the synthesis of matrix proteins is most active. In heart the levels of these mRNAs peaked at day 12. In addition, qualitative differences were observed in the expression of actin genes between tendon and heart. Dexamethasone in high dose decreased collagen mRNA levels in tendons, while in heart a stimulatory effect was noted. Dexamethasone also decreased GAPDH mRNA levels in tendons. The alterations in gene expression after dexamethasone treatment in tendon and heart did not correlate with the level of specific glucocorticoid receptors, which varied markedly during the development of chick embryos. The cDNA for pro alpha 1(I) collagen hybridized to two transcripts corresponding to 6.2 and 5.1 kb in tendon and heart. During normal development of chick embryos the ratio of 6.2/5.1 kb mRNAs decreased markedly in heart, but no such change was observed in tendons. Dexamethasone, however, decreased the ratio of 6.2/5.1 kb transcripts in tendons. There was a significant correlation between the ratio 6.2/5.1 kb transcripts and total alpha 1(I) mRNA both in tendon and heart, suggesting that the 6.2 kb transcript may be associated with the rate of synthesis of type I collagen.

Quantitative changes in cytoskeletal beta- and gamma-actin mRNAs and apparent absence of sarcomeric actin gene transcripts in early mouse embryos

Actin is known to be synthesized both during oogenesis and in cleavage-stage embryos in mice. Cytoskeletal beta-actin appears to be the major component, followed by gamma-actin, but the synthesis of alpha-actin has also been inferred from protein electrophoretic patterns. We have studied the expression of cytoskeletal (beta- and gamma-) and sarcomeric (alpha-cardiac and alpha-skeletal) actin genes at the level of the individual mRNAs in blot hybridization experiments using isoform-specific RNA probes. The results show that there are about 2 x 10(4) beta-actin mRNA molecules in the fully grown oocyte; this number drops to about one-half in the egg and less than one-tenth in the late two-cell embryo but increases rapidly during cleavage to about 3 x 10(5) molecules in the late blastocyst. The amount of gamma-actin mRNA is similar to that of beta-actin in oocytes and eggs but only about 40% as much in late blastocysts, indicating a differential accumulation of these mRNAs during cleavage. The developmental pattern of beta- and gamma-actin mRNA provides a striking example of the transition from maternal to embryonic control that occurs at the two-cell stage and involves the elimination of most or all of the maternal actin mRNA. There was no detectable alpha-cardiac or alpha-skeletal mRNA (i.e., less than 1,000 molecules per embryo) at any stage from oocyte to late blastocyst, suggesting that the sarcomeric actin genes are silent during preimplantation development.

Phenol red mimics biological actions of estradiol: enhancement of osteoblast proliferation in vitro and of type I collagen gene expression in bone and uterus of rats in vivo

Since osteoblasts are direct targets for estradiol in vitro, and Phenol Red has been reported to bear estrogen-like bioactivity, we investigated whether the pH indicator also mimicked the biological effects of estradiol on bone cells in vitro. We then asked whether estrogenic effects of Phenol Red could be observed in vivo, firstly on the uterus, and if so, whether Phenol Red could also effect bone in vivo. The proliferation of calvarial osteoblasts was stimulated by commercially available preparations of Phenol Red in a dose-dependent manner at 1.5-50 microM. This effect was not abolished in the presence of an antibody against insulin-like growth factor I. In addition, Phenol Red increased alpha 1 (I) collagen mRNA levels of osteoblasts in vitro. 17 beta-estradiol (1.5 micrograms) or Phenol Red (10 mg) administration to immature female rats (45-50 g) resulted in a weight gain of the uterus, and alpha 1(I) procollagen transcripts were more abundant in RNA prepared from uterus of drug-treated rats than observed in the control rats. Similarly, higher procollagen mRNA steady-state levels were observed in RNA prepared from parietal bones of Phenol Red or estradiol-treated rats compared to RNA from control rats. The data extend previous findings in vitro by demonstrating that Phenol Red also exerts estrogen-like effects in vivo. Moreover, we show that Phenol Red stimulates bone cells and, therefore, is likely to interfere at least in experiments designed to investigate estrogen effects on osteoblasts.

Alpha-smooth muscle actin is expressed in a subset of bone marrow stromal cells in normal and pathological conditions

A series of 217 trephine bone marrow biopsies from adult patients and specimens from 16 fetuses and 5 infants were examined for the presence of stromal myoid cells (MCs) using a monoclonal antibody recognizing alpha-smooth muscle actin. In the normal adult bone marrow, stromal cells did not contain alpha-smooth muscle actin, whereas during fetal life, many alpha-smooth muscle actin-containing MCs were connected with vascular sinusoids in the primitive bone marrow. This cell type reappeared in various characteristic distribution patterns in adult bone marrow during different neoplastic and non-neoplastic conditions including metastatic carcinoma, Hodgkin's disease, multiple myeloma, hairy cell leukemia, acute myeloid leukemia (FAB M4, 5, 7) and chronic myelo-proliferative diseases. In general, the appearance of MCs was associated with a slight to pronounced increase in the deposition of reticulin and collagen fibers. We propose that bone marrow MCs represent a distinct subpopulation of fiber-associated or adventitial reticular cells undergoing cytoskeletal remodeling in response to various stimuli.

Alpha smooth muscle actin (alpha-SM actin) in normal human ovaries, in ovarian stromal hyperplasia and in ovarian neoplasms

An immunohistochemical investigation of alpha-smooth muscle actin (alpha-SM actin) using the monoclonal anti-alpha-SM-1 antibody was carried out in 15 normal ovaries, in three ovaries with stromal hyperplasia and in 27 neoplastic ovaries. In selected cases the pattern of actin isoforms was examined by means of 2 D-gel electrophoresis. In addition, the tissues were stained for vimentin and desmin. In normal ovaries alpha-SM actin was found in the inner cortex and in the theca externa. In ovarian stromal hyperplasia expression of alpha-SM actin was minimal or absent. In primary and metastatic epithelial tumors there was positive stromal staining for alpha-SM actin, especially in the vicinity of epithelial elements. This tended to be more widespread in malignant neoplasms. Thecomas did not express alpha-SM-actin and could thus be differentiated from leiomyomas which stained intensely for alpha-SM actin. Only focal stromal staining of alpha-SM actin was observed in granulosa and germ cell tumors. In all the tissues studied blood vessels were strongly positive for alpha-SM actin. Desmin, although present in the stroma of most of the specimens, was less abundant than alpha-SM actin. We concluded that alpha-SM actin is a component of the normal human ovary where it may contribute to the contractility of its stroma. Its absence in the normal outer cortex and theca interna, and in stromal hyperplasia and thecoma implies that sex hormones do not constitute a stimulus for alpha-SM actin production in the ovary. Among neoplasms it is most widely represented in the stroma of epithelial tumors in which it may reflect stromal stimulation mediated by neoplastic epithelium.

Conserved and unique sequences in the 3'-untranslated region of rat smooth-muscle alpha-actin mRNA

We have isolated a cDNA clone corresponding to rat smooth-muscle alpha-actin mRNA [Hsu and Frankel, J. Biol. Chem. 262 (1987) 9594-9600]. We present here the sequence of the 3'-untranslated region (3'-UTR) of the cDNA. By comparison with the reported sequence of the chicken gene, this 3'-UTR region contains a conserved 36-bp sequence and a unique 48-bp G + C-rich sequence. An RNA probe containing only the 3'-UTR of the cDNA was synthesized and shown to be specific for smooth-muscle alpha-actin message.